add_image_size( 'staff', 400, 270, true );
add_image_size( 'staff_full', 500, 340, true );
According to the element you are using (portfolio, blog, staff..etc) edit the respective image sizes here. So, if you are using portfolio with two columns, edit:add_image_size( 'port2', 825, 340, true );
If you are using portfolio 3 columns with grayscale, edit this:add_image_size( 'port3_grayscale', 627, 470, true );.
After that you should recreate the images thumbnails (run a plugin that does this) or reupload the images.